Photoresist masks are commonly used in the semiconductor industry to pattern materials such as semiconductors or dielectrics. In one well-known application, photoresist masks are used in a dual damascene process to form metal interconnects during the back end of line (BEOL) metallization of a semiconductor device. The dual damascene process involves formation of a photoresist mask on a dielectric layer overlying a metal contact structure or metal conductor layer, such as a copper layer. The dielectric layer is then etched according to the photoresist mask to form a via and/or trench that expose the underlying metal contact structure or metal conductor layer. The via and trench, collectively known as dual damascene structure, are typically defined using two lithography steps. After the lithography steps are performed, the photoresist mask is removed from the dielectric layer before a conductive material is deposited into the via and/or trench to form an interconnect.
As scaling of semiconductor devices continues, it becomes more difficult to achieve the necessary critical dimensions for vias and trenches. Thus, metal hard masks are increasingly used to provide better profile control of vias and trenches. The metal hard masks are typically made of titanium (Ti) or titanium nitride (TiN). A wet etching process is normally performed after forming the via and/or trench of the dual damascene structure to remove the metal hard mask. In the conventional process, it is desirable that the wet etching process use an etchant chemistry that effectively removes the metal hard mask without affecting the underlying metal conductor layer and dielectric material. In other words, the etchant chemistry is required to etch the metal hard mask at a much faster rate than it etches the metal conductor layer and dielectric layer.
However, titanium nitride is commonly used as both a metal hard mask and as a barrier metal in metal contact structures. Therefore, it may be difficult or impossible to use a wet etchant to selectively remove titanium nitride hard masks after performing a dual damascene process that exposes a metal contact structure including a titanium nitride barrier metal. Specifically, the etchant will attack and form voids in the metal contact structure during removal of the metal hard mask. Alternatively, the same metals cannot be used for the metal hard mask and in the metal contact structure.
Accordingly, it is desirable to provide improved integrated circuits and improved methods for fabricating integrated circuits that facilitate removal of metal hard masks while avoiding attack of the underlying metal contact structure. In addition, it is desirable to provide integrated circuits and methods for fabricating integrated circuits that form capping layers between metal contact structures and metal interconnect structures. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.